Abstract
Deep eutectic solvents (DESs) are green solvents developed as an alternative to conventional organic solvents and ionic liquids to extract nitrogen compounds from fuel oil. DESs based on p-toluenesulfonic acid (PTSA) are a new solvent class still under investigation for extraction/separation. This study investigated a new DES formed from a combination of tetrabutylphosphonium bromide (TBPBr) and PTSA at a 1:1 molar ratio. Two sets of ternary liquid–liquid equilibrium experiments were performed with different feed concentrations of nitrogen compounds ranging up to 20 mol% in gasoline and diesel model fuel oils. More than 99% of quinoline was extracted from heptane and pentadecane using the DES, leaving the minutest amount of the contaminant. Selectivity was up to 11,000 for the heptane system and up to 24,000 for the pentadecane system at room temperature. The raffinate phase’s proton nuclear magnetic resonance (1H-NMR) spectroscopy and GC analysis identified a significantly small amount of quinoline. The selectivity toward quinoline was significantly high at low solute concentrations. The root-mean-square deviation between experimental data and the non-random two-liquid (NRTL) model was 1.12% and 0.31% with heptane and pentadecane, respectively. The results showed that the TBPBr/PTSADES is considerably efficient in eliminating nitrogen compounds from fuel oil.
Highlights
Nitrogen and sulfur compounds are harmful to the environment and the health of living organisms, including human and aquatic lives
This study developed a green, low-cost Deep eutectic solvents (DESs) comprising tetrabutylphosphonium bromide (TBPBr) and p-toluenesulfonic acid (PTSA) and investigated for the first time its performance related to the extraction of nitrogen compounds from fuel oil
The TBPBr:PTSA DES with a 1:1 molar ratio formed a yellow liquid upon heating and remained a liquid at room temperature after 24 h
Summary
Nitrogen and sulfur compounds are harmful to the environment and the health of living organisms, including human and aquatic lives. Even a small amount of basic nitrogen compounds can lead to fuel oil having >10 ppm of sulfur content [2,3] They are a precursor for coke formation in hydroprocessing units [4]. Most of the organic solvents are efficient in extraction processes [11] Their physical properties, such as high volatility, low thermal and chemical stability, and toxicity hinder their potential to be widely used on an industrial scale [12,13,14]. The same DES shows a high selectivity of 3606 toward indoline, which is a non-basic nitrogen compound These findings are in agreement with Hizaddin et al, who reported that phosphonium-based DESs can be potential solvents for extracting nitrogen compounds [17]. We reported the physical properties of the TBPBr:PTSA 1:1 DES
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